Shamefaced
/ˌʃeɪmˈfeɪst/
Definition 1 of 1
Pro Tip 1/3Showing Guilt
Use 'shamefaced' when someone looks guilty and is sorry for what they've done. 
His shamefaced expression revealed his remorse.
Pro Tip 2/3Lack of Confidence
'Shamefaced' also describes someone who is not feeling confident or proud at that moment. 
He was shamefaced when he received criticism for his work.
Pro Tip 3/3Personal Emotions
The word often relates to personal emotions rather than a public occurrence. 
She felt shamefaced after forgetting her friend's birthday.